The answer to 'when to replace circuit breaker' is that you should replace a circuit breaker when it is no longer functioning properly or has reached the end of its lifespan. Circuit breakers are designed to last for many years, but they can wear out over time due to repeated use, exposure to electrical surges, or other factors.
Signs that a circuit breaker may need to be replaced include frequent tripping, difficulty resetting the breaker, or visible damage or wear. If a circuit breaker is not working reliably, it's important to have it inspected and replaced by a qualified electrician to ensure the safety of your home's electrical system.